What to do if your car heater isn't working

While it’s normal for air con to stop working at the most inconvenient times (midsummer noon in a traffic jam) – if your car’s heater stops working then you should pay attention: it could indicate a more serious problem. So don’t put off car checks if your car heater’s blowing out cold air.

Let’s first quickly look at how a heater works.

How does a car heater work?

We’ll not go into the complete technical detail, but it’s worth knowing that your air con and heating system are related. Essentially, they’re both ways of using the heat and power generated by your engine to either cool or warm air that’s circulated around your vehicle.

Air con works slightly differently in that you need a refrigerant to get the air lower than the ambient air temperature, but car heaters are (in most vehicles) essentially just the engine.

The engine needs to get up to a certain operating temperature to run most efficiently, but after a certain point it’s liable to overheat. Original car designs featured grills to cool the engine with air directed to it while the car drives – but what about when you’re stuck in traffic? Or what about when it’s an extremely hot summer’s day?

Quite soon, liquid cooling was invented to help regulate engines at all times.

The fundamental concept here is that a coolant liquid is pumped through tubes that are around the engine, the liquid is warmed by the heat of the engine (therefore taking heat out of the engine), and then it is released somewhere through the use of a radiator.

The coolant liquid here forms a closed loop system, so as it circulates it’s constantly drawing heat away from the engine.

Car heaters are an extra addition to this loop. The idea is that an extra radiator is added into the loop – that radiator is placed in front of a fan that pulls air into the ducts (either from the outside or from inside the car) and past the radiator into the vehicle itself. As the cold air passes over the now-hot radiator, it’s warmed up.

This is why it often takes a few minutes for the heating in your car to get going – because it takes a few minutes for the engine and coolant to get warm!

What does it mean if your car heating stops working?

It can mean a few things depending on which part seems to have stopped working.

1.) The fan may have broken or the ducts may have become blocked

If you’ve turned the heating on but there’s no air coming through open ducts, then there’s a good chance that the problem lies with the radiator fan. Check the air grills around the outside of your car, specifically around the air intake vent.

2.) There could be a coolant leak

If the fans are running as normal at all powers, then you need to check your coolant reservoir to make sure the coolant level hasn’t dropped. If the air isn’t getting hot then it’s possible that the coolant has leaked to a point where there’s not enough to even cool the engine.

In this situation, your first step should be to turn off the engine and try topping up the reservoir (slowly) with more coolant.

Hopefully, it’ll only be a slow leak so that you’ve got time to get to a service centre!

If the coolant quickly drains then you’ve got a bigger problem on your hands because you shouldn’t drive your car without coolant – an overheated engine is potentially a much more costly fix than a few pipes!

Your best bet here is to call for emergency assistance to have your car towed to an auto centre.

Trust the experts at your local Kwik Fit centre

We hope you never have to call for roadside assistance, and we strive to help you never need to through our range of services: from 6-monthly checkups to full-blown part replacements, you can trust the experts at your local Kwik Fit to keep your car sturdy.